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Another consideration is the electrolyte freezing point. A
fully charged battery can withstand temperatures of -60
to -90° F since the electrolyte’s specific gravity is at a
proper level. Conversely, the electrolyte in a weak or
discharged battery may freeze at temperatures near 32°
F. If a fully charged battery is depleted by an unsuccessful
start, it may freeze as it cools to ambient
temperature. Later, when the engine is started and the
battery is receiving a charge, it could explode.
After start, a proper warmup should be completed
prior to a runup and high power settings. Perform
the warmup according to the engine manufacturer’s
recommendations. Some manufacturers
recommend a minimum of 1,000 r.p.m. to ensure
adequate lubrication.
If the skiplane is parked on heavily crusted snow or
glaze ice with the skis frozen to the surface, it may be
possible to start the engine and perform the runup in
the parking area. Be sure the area behind the skiplane
is clear, so as not to cause damage with the propeller
wash. If a ski should become unstuck during the
runup, reduce power immediately. Then use one of the
following procedures to secure the airplane.
Tie down or chock the skiplane prior to engine start,
warmup, and runup. Keep all ropes, bags, etc., clear of
the propeller. After warmup is complete, and if no
assistance is available, shut down the engine to untie
and unchock the skiplane, then restart as quickly as
possible. If a post, tree, boulder, or other suitable
object is available, tie a rope to an accessible structural
component in the cockpit, take the end around the
anchor object, bring it back to the cockpit, and tie it off
with a quick-release knot. When the warmup and
runup are complete, release the knot and pull the rope
into the cockpit as the skiplane begins to taxi.
If tiedowns or chocks are not available, build small
mounds of snow in front of each ski. The mounds must
be large enough to prevent the skiplane from taxiing
over them during engine start and warmup, but small
enough to allow taxiing when power is applied after
the warmup is complete. If tiedowns or means to block
the skis are not available, the runup can be accomplished
while taxiing when clear of obstacles or other
hazards. [Figure 7-4]
Figure 7-4. Engine warmup.
Ch 07.qxd 8/25/04 11:20 AM Page 7-4
7-5
TAXIING
Taxiing a skiplane on snow and ice presents some
unusual challenges. With little or no brakes for stopping
or turning, and the ability to skid sideways, a
skiplane normally requires more maneuvering room
and space to turn than an airplane with wheels.
The tailwheel ski provides marginal directional control
on ice and hard packed snow. In such conditions, directional
control comes from airflow over the rudder.
Adding power and forward elevator control pressure
can often help turn the skiplane. The goal is to lighten
the tail to help the turn without putting the skiplane on
its nose.
Taxiing in strong crosswinds can be difficult. Skiplanes
tend to weathervane into the wind. Drifting sideways in
the direction of the wind is also commonplace. Taxi in
a skid or let the skiplane weathervane partly into the
wind during crosswind operations to compensate.
[Figure 7-5] A short blast of power may be required to
turn the skiplane from upwind to downwind. It is normal
to drift sideways in turns. Preplan the taxi track so
as to remain clear of drifts, ridges, or other
obstructions.
When taxiing in crosswinds on glare ice, get a helper at
each wingtip to help with turns and aligning the
skiplane for takeoff.
As a general rule, power settings and taxi speeds should
be kept as low as possible on ice or crusted snow. On
loose or powder snow, add enough power to maintain
forward motion and keep the skis on top of the snow.
The skiplane may even be step-taxied in a manner similar
to a floatplane, staying below takeoff speed. If the
skiplane is allowed to sink into soft snow, it may stop
moving and become stuck. When the snow is wet and
sticky, work the rudder and elevator to get the skiplane
moving and maintain forward motion to prevent the
skis from sticking again. If the skis are freed during
preflight, but stick again before starting the engine and
beginning to taxi, free the skis again and pull the
skiplane onto tree branches, leaves, or anything that
will prevent the skis from sticking. Burlap bags can
be used by tying a line to the bags and pulling them
into the cockpit after the skiplane has taxied forward.
Keep all ropes, bags, etc., clear of the propeller. Rapid
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